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HT08/P1 IK1500 2
Content
• Elements of networking– Multiplexing– Switching– Routing– Network management (not discussed in this
course).
• Problem solving
HT08/P1 IK1500 3
Distributed information applications
source/sink
source/sink
source/sink
source/sink
source/sink
source/sink
Distributedinformation applications
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Examples of Sources/Sinks
• Sources– Telephone– Video cameras– Files on a disk
• Sinks– Telephone receivers– Television monitors– Computer storage devices
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Layered Model
Bit Carrier Infrastructure
Resource Sharing Mechanisms
sources and/or sinksnetworked applications
Common Information Services
Multiplexing, scheduling, routing,network management
Information services
Communication links
infrastructure and traffic flow :
buffering, jitter removal, etc.browsers, source compression, storage,User interfaces, transducers, servers,
Dynamic and intelligent control of
Networking
WDM, Optical crossconnects, SDH, DSL,cable, Ethernet, satellite, fixed or mobilewireless links
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Layered Model
• Information Services– e.g. Packet telephony, electronic mail, www
• Networking– Quality of Service requirements– Resource sharing
• Communication Links– Regarded in this course as imperfect bit-pipes:
They can delay, lose or modify the information they carry
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Quality of Service
• Certain Quality of Service (QoS) e.g. in terms of:– Guaranteed bounds of service denial– Statistical bounds of service denial– Information loss– Throughput– Delay
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Design Perspectives
• Communication Link– Highest possible bit transmission rate (given
the resources used)– Acceptable bit rate
• Networking– QoS requirements for the flows may be
different for different applications:• Short delay but can tolerate higher bit error rates• Reliable transfer and high throughput
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Comparison: Networking – OS
Distributedalgorithms for
information transport(e.g., X.25, Internet, ATM)
Applications
Computeroperating system
(e.g., Unix, Linux, Windows)
Network ofcommunication links
Hardware(e.g., processor, memory,disk drives, sound card)
(e.g., calculation, accounting,database)
Distributedinformationapplications
(e.g., www, e-commerce, teleconf)
Protocols
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Functional Elements
• Multiplexing
• Switching
• Routing
• Network management
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Multiplexing
• Circuit Multiplexing– Link transmission rate is divided into channels– Each conversation gets one channel and holds that
channel for the duration of the connection– Rate is fixed at connection setup time– If there are no available channels then the new
communication reqeust is blocked
• Main performance objectives:– Probability of blocking– Handling of different classes of flows
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Circuit multiplexing
time
channelslink
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Traffic Flow
data emitted by a computer
PCM (pulse coded modulation)voice with activity detection
variable-bit-rate video
video frames (e.g., 30 frames/sec)
talk spurt silence
random epochs of data emission
bit rate
scenechange
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Multiplexing
• Packet Multiplexing– Average rate must be less than the bit rate of the link– Peak rate can exceed the link’s bit rate
• Excess data must be queued delay• If the buffer is to small data loss
– Overhead• Header (and in certain cases a Trailer)
• Main performance objectives:– Low probability of loss– Bounded delay
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Packet Multiplexing
time
link
packets from various connections
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Multiplexing Taxonomy
multiplexing
circuit multiplexed packet multiplexed
centralized distributed
randomaccess
polledaccess
reservationaccess
token passingmaster-slave
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Centralized Packet Multiplexing
Terminal
Terminal
Terminal
Terminal
Host
Host
Multiplexer Multiplexer
multiplexer ports
full-duplex link
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Distributed Packet Multiplexing
link
Nodes
Random Access
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Polling Based Distributed Packet Multiplexing
Node
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Reservation Based Distributed Packet Multiplexing
VSAT
VSAT
Router
RouterCampusnetwork
Campusnetwork
Packetswitch
DIU
DIU
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Hybrid Link Multiplexing
movableboundary
circuit-multiplexed
packet-multiplexed
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Six-Node Network
S2S1
S
(c)
(b)(a)
links2
)1( NNN links
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Switch
Switchlink
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Switch Functionality
• Demultiplexing each flow
• Determine the output link for the flow
• Forward (switch) the element of each flow to the right output link
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Packet Switch
• Store-and-forward– Receive the entire packet first, then forward it
• Cut-through– Start forwarding the packet as soon as it
arrives
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Packet Switch
O/p Queuescheduling,processing
O/p queuescheduling,processing
Control and signaling functions
Switchfabric
Queueing andscheduling
Queueing andscheduling
Input processingand forwarding
Input processingand forwarding
Lineinterface
Lineinterface
Lineinterface
Lineinterface
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Call Setup Procedure for a Circuit Multiplexed Network
call teardown delay
call-processing delay
dial tone delay
information transfer
calling phone switch
call complete signal (on hook)
dial digits
apply dial tone
phone goes off hook
call accept (or deny) signal
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Operation of a Circuit Switch
input i x
TDM frame TDM frame
Control processor
output oy
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Routing
• Establish paths through the network between sources and sinks
• Difference between routing and forwarding
• Two types:– Centralized Routing– Distributed Routing
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Routing
• Routing Algorithms– Find end-to-end path through the networks– While:
• Fulfilling QoS constraints• Utilize network resources efficiently
• Two main types:– Hop-by-Hop routing– Source routing
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Packet Multiplexed Network
• Virtual circuit-based– Routes are determined at the connection
setup time – Sufficient to know the label of the connection
and not the complete source and destination address
• Datagram-based– Each packet is routed separately– Each packet must know the source and
destination address
